Systems comprising shafts which are constructed for slideable linear motion in cylindrical bearings are subject to a high degree of friction, and wear, binding and chatter because of misalignment, which lead to lubrication and maintenance problems.
Attempts have been made to reduce or eliminate some of the problems in such systems by using one or more oblong re-circulation ball circuits or Roundway bearings which circulate in the longitudinal direction of the shaft.
Such systems have certain disadvantages, in that they are heavy, requiring a substantial amount of additional material; and the circulating ball or roller trains retain dirt and foreign particles. Furthermore, they exert extreme pressures at the points of contact on the shaft which cause what is known as `brinelling` in which the material of the shaft flakes away. Further, such systems cause excessive wear at contact points on the shaft.
A linear motion pillow block is disclosed in U.S. Pat. No. 4,715,730, hereby incorporated by reference. This disclosure includes a description of a pillow block having a self-aligning feature. The self-aligning feature is described, for example, at Column 5, line 47 through Column 6, line 34. The self-aligned feature includes a bearing which is connected to an eccentric cylinder stud. The device can be fine tuned by turning the eccentric cylinder stud to cause the circumferential surface of the bearing to move radially toward the surface of the shaft passing through the primary bore of the pillow block.